The correct interpretation is that for prefix 10.1.1.1/32, the router will pop the MPLS label before forwarding because the outgoing label is 'Pop Label'. This operation, known as Penultimate Hop Popping (PHP), occurs when the penultimate router removes the label so the egress router receives a pure IP packet, reducing its processing load. The show mpls forwarding-table output meaning pop label is critical for the ENCOR 350-401 exam, as it tests your ability to read label operations—swap, pop, or untagged—and understand how they map to MPLS forwarding behavior. A common trap is confusing 'Pop Label' with 'Untagged'; remember that 'Pop' removes the top label and forwards the remaining packet, while 'Untagged' means the packet exits the MPLS domain without any label. For the exam, focus on the outgoing label column: if it says 'Pop Label', the router performs PHP; if it says a number, it swaps; if 'Untagged', it strips all labels. Memory tip: "Pop goes the label, Untagged leaves the MPLS stable."
350-401 MPLS Practice Question
This 350-401 practice question tests your understanding of mpls. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer runs the following command on Router R2:
R2# show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
16 Pop Label 10.1.1.1/32 0 Gi0/0 192.168.1.1
17 18 10.2.2.0/24 1500 Gi0/1 192.168.2.3
18 Untagged 10.3.3.0/24 0 Gi0/2 192.168.3.4
Based on this output, what is the correct interpretation?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
For prefix 10.1.1.1/32, the router will pop the MPLS label before forwarding because the outgoing label is 'Pop Label'.
The forwarding table shows label operations. For prefix 10.1.1.1/32, the outgoing label is 'Pop Label' meaning PHP (Penultimate Hop Popping). For 10.2.2.0/24, label 17 is swapped to 18. For 10.3.3.0/24, 'Untagged' means the packet is forwarded without an MPLS label (e.g., to a non-MPLS interface).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
For prefix 10.1.1.1/32, the router will pop the MPLS label before forwarding because the outgoing label is 'Pop Label'.
Why this is correct
Pop Label indicates PHP, so the router removes the label.
Related concept
Read the scenario before looking for a memorised answer.
✗
For prefix 10.2.2.0/24, the router will impose label 18 onto the packet.
Why it's wrong here
The outgoing label is 18, meaning it swaps the incoming label 17 to 18, not imposes a new label.
✗
For prefix 10.3.3.0/24, the router will forward the packet with an MPLS label of 18.
Why it's wrong here
The output says 'Untagged', meaning no label is used.
✗
The router has received 1500 bytes for prefix 10.2.2.0/24, and the outgoing interface is Gi0/1.
Why it's wrong here
Bytes Label Switched is 1500, meaning 1500 bytes have been switched with that label, not received.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
The output says 'Untagged', meaning no label is used.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
MPLS — This question tests MPLS — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: For prefix 10.1.1.1/32, the router will pop the MPLS label before forwarding because the outgoing label is 'Pop Label'. — The forwarding table shows label operations. For prefix 10.1.1.1/32, the outgoing label is 'Pop Label' meaning PHP (Penultimate Hop Popping). For 10.2.2.0/24, label 17 is swapped to 18. For 10.3.3.0/24, 'Untagged' means the packet is forwarded without an MPLS label (e.g., to a non-MPLS interface).
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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